Automatic telephone system



1,624, 2 April l2 1927' J. E. GARDNER 3 AUTOMATIC TELEPHONE SYSTEM Original Filed March '7, 1922 1 JUE-E Eapd Patented Apr'. 12, 1927.

UNITED STATES JOHN GABDIIER, OF CHCAG, ULL" n, ASSG'NR, BY MESH-E A'SSGNMENTS, TO

AUTOMATIC ELECTRIC NC., OF Cs-CAGG, liLNOS, A CORPORATION OF DELA:-

AUTOMATIC TELEHONE SYSTEM.

Appneation alsa March 7, 1922, sensi The present invention relates in general to automatic telephone systems, but is more particularly concerned with small automatic exchange systems ot a type which have come into extended commercial use in manufacturing plants, mercantile establishments, and the like.

More specifically, the present invention is concerned with small private automatic exchange systems of one hundred lines or less in which each subscriber has an individual line switch which has access to loc-al connector switches of a new design, and the general object of the invention is to arrange the circuits ota system ot this character so that it may be readily enlarged to accommodate additional lines witn little or no change in the existingequipment, and with the addition or but another group of connector lswitches. Heretotorc, in order to increase the size of a one hundred line connector system the ordinary method involved the installation et selector switches and a change in tlnltrunkin-got the existing equipment so that the subscribers line switches, instead ot having direct access to the connector switches, had access to selector switches. these selectors in turn having;l access to two groups of connector switches. 'lhe present invention provides novel circuit arrangements for accomplishing the same results without the addition of selector switches it is, ot course, obvious that the scheme used herein maybe installed originally it a system larger than 100 lines is desired. Y v

There are other objects of the invention not now specifically mentioned, which, together with the toregoing will be described hereinafter, reference being had to the acn companying` drawing forming part ot' this s;wcitication.

Referring` now to the igure of drawing, there is shown by means of the conventional circuit diagrams enough ot the apparatus to illustrate the invention. This includes a calling substation A, a line switch C, a connector H and a called substation A.

The subscribers substation A is ot the ordinaryY automatic type, having,` the usual talking` instrumentalitiesA` and in addition an automatic calling device S. The line of the substation A. terminates at the exchange in No. 541,780. Renewed August 12, 1926.

an individual line or trunk selecting switch rlhe line switch C is ot the usual rotary type, whose wipers are always in engagement when idle with the bank contacts associated with the trunk line last used. The line switch C, in common with a plurality ot other lin-e switches, has access to trunk lines hauling to local connector switches, one of the latter being` shown at H. n .lhe connector lvl is similar to the usual fjtrowger switch ot' the vertical and rotary type. However, this connector diiers from the ordinary construction in that it is provided with an extra level of bank contacts, making all together a total of eleven levels instead of ten. The connector is so arranged that its wipers are always standingl .opposite the tirst level o't bank .contacts which is thus a kind et normal level. The connector H has access to local subscribers line, the substation associated with one of these being shown in the drawings at A.

Yielays such as 5l and 52 are slow to release, this beingl indicated by the cross hatching on their cores. Relays such as lt and 162 are both slow to pull and slow to release, these relays being,` distinguished from the `former type by showing` the ends of the cores in solid black The line ot' the substation A terminates at the exchange in the individual line switch C which is similar to the line switch C already described.

In order to describe the present invention it will be assumed that the private automatic exchange system about to be described has a capacity ot ninety lines and it is desired to increase it to a larger system of 180 lines. it will be assumed further that this private automatic exchange has trunk lines leading` from it to a main automatic exchange, so that subscribers in the private automatic exchange may extend calls to subscribers in Jthe .main automatic exchange. Vf e will iii-st consider the ordinary operation of the system betere it is enlarged. In order to do this the mannerv in which a call extended from the subscriber at the substation A to the subscriber at the substation A will rstbe described. To extend a call to the substation A/ the subscriber at substation A will remove his receiver' and oper- Cil `ate his calling device for the two digits which includes the switching relay l5 and the motor magnet 16 in series, and at its armature 2O connects the test wiper 26 to the above circuit at a point midway between the switching relay and the said motor mag net. The operation of the line switch C now depends upon whether its wipers are associated with a busy trunk line or not. It the associated trunk line is busy there will be a ground potential present upon the test contact engaged by the test wiper 26, switching relay l5 will be short circuited, and the motor magnet 16, being supplied with direct ground by way of the said test wiper, will 'operate as a buzzer to advance the switch wipers 27, inclusive, step by step in search ot Van idle trunk line. However, in the present instance it will be assumed that when the receiver is removed at substation L the trunk line leading from the bank contacts associated withthe wipers of the line Vswitch C is idle, and it will be assumed turther that this'atrunk line is the one shown in the drawing terminating in the bank contacts e-32, inclusive. Under these conditions there will be no ground potential on the test contact 3l engaged by the test wiper 2G, and the switching relay l5 will be energized immediately after the energization ot the line relay lst. Relay l5, upon energizing, at its armature 1S places ground upon the test contact 3l to prevent the trunk line seized 'from being used for another call, and at its armatures 17 and 19 disconnects the line conductors ll and l2 oit' the substation A :l'rom the winding of the line relay ld and from ground, respectively, and extends them by way ot armatures 17 and 19, wipers 25 and bank contacts 30 and 32 to the upper and lower windings ot' the line relay ot' the connector il.

The line relay is immediately energized over the calling line loop and, upon operating, at its armature 65 closes the circuit ot its associated slow-acting release relay l. rlhe latter relay, `upon energizing, at armature (3S opensv one point in the circuit ot the release magnet, at the front contact of this armature prepares the impulsing circuits of the connector H, and at armature (37 places ground upon the release trunk conductor a9, thereby establishing a holding circuit tor the line switch C. rlhis holding circuit may be traced from ground on the release conductor 49 by way oli' test contact Bl, test wiper 26, armature 18 and its front contact, through the winding of the switch- Lee/isaeing relay l5, and thence through the windn .ing of the motor magnet 1G to battery. rlhis holding circuit serves to maintain the switching relay l5 energized throughout the connection and it will be understood that it is established before the slow-acting lino relay let has had time to deenergize. n branch of this holding circuit extends by way of the private normal conductor 29 to multiple test contacts in the banks ot' the local connector switches such as H, whereby the line ot the substation A is protected trom intrusion during the existence otl the connection.

The calling subscriber at substation A may now operate his calling device S for the lirst digit of the desired number thereby producing a series of interruptions in the circuit ot the line relay 50. In response to the interruptions in its circuit the line relay deenergizes a plurality ot times each time sending an impulse ot current over the following circuit: ground by way ot armature 65 and its back contact, armature 68 and its front contact, oliil normal springs (59 and 7l, through the winding of the slow acting low resistance relay 52, and through the winding ot the vertical magnet to battery. The above is the circuit over which the lirst impulse is sent to the vertical magnet. However, upon the iirst vertical step of the switch shat't the otiA normal springs are shifted and the remaining vertical magnet impulses traverse a new circuit which is the same as the one previously traced except that it includes the off normal springs 69 and 7 0,`and armature 7 5 and yits front contact, the relay 52 being now in an operated position. Magnet (30 operates to raise the switch shaft carrying the wipers UQAM, inclusive,step by step until they are brought opposite the level or' bank contacts corresponding to theV digit dialed. The slow acting relay 52 is energized in series with the vertical magnet, maintains its armature attracted throughoutthe vertical movement of the switch and at the termination thereof deenergizes thereby transferring the impulsing circuit to the rotary magnet 62.

lVhen the calling device at substation A is operated in accordance with the next and final digit of the desired number, anotherl series of interruptions is produced in the circuit of line relay 50 thereby causing this relay to deenergize a corresponding number ot times. At each retraction of its armature (55, an impulse ot' current is sent over a circuit extending trom ground through armature and its back contact, armature G8 and its tront contact, ott' normal springs 69 and 70, armature and its back Contact, normally closed springs controlled by armature 88, armature 108 and its back contact, and thence through the winding ot the rotary magnet G2 to battery Rotary mag lori net GQ operates to rotate the switch wipers 112-11Ll, inclusive, into engagement with the set otl bank contacts associated with the line ot the desired called subscriber at substation A', and which we will assume are the bank contacts 123125, inclusive. The slow acting relay T is energized in multiple with the rotary magnet G2. llelay 5T, upon energizing, at its armature 923 short circuits the springs controlled by armature 8S in order to preserve the continuity ot the rotary magnet circuit while the switch wipers are being rotated over bank contact sets associated with busy lines, and at its armature 02 connects the test wiper 113-3 to the test relay 56. rlhe attraction ot' armature 01 of relay :3T is without function at the present time. The operation ot' the connector' H now depends upon whether the line of the substation is busy or not.

lt will tirst be assumed that the line ot the substation is busy. Under these conditions there will be a ground potential present upon the test contact 12st engaged by the test wiper 113. A circuit is thereupon conipleted extending troni said grounded test contact by way ot the said test wiper, normally closed springs controlled by armature T, armature 02 and its trent contact. arma ture 9i) and its back contact and through Vthe winding ot the test relay to battery. lrelay 56 is immediately energized over this circuit and. upon operating, at its armature Si establishes a locking circuit tor itself, at armature S8 opens the lircuit ot the rotary magnet Gir, and at armature connects a lead from the busy signalling machine to the lower heavy talking conductor. This tone is audible to the calling subscriber at substation ci who will replace his receiver as he knows that the called line is inaccessible at the present time. The replacementy ot the receiver at subsation )i causes the release ot the connector H and line switch C in a n anne which will be described hereina'l'ter.

lt will now be assumed that the line ot the substation A is idle when the wipers ot' the connector H are rotated into engagement with the associated contact set com- Irising contacts 1225-125, inclusive. Then this occurs there will be no ground potential upon the test contact engaged by the test wiper 113 and the test relay 5G will not be energized. Then. immediately following the decnergization ot the slow acting relay 5T. a circuit is completed which extends trom ground on release conductor lt) by way ot armature ST and its back contact, through the upper winding oit the relay of), through the upper winding ot relay 5S, back contact and armature 92. normally closed springs controlled by armature 10T, test wiper 113, test contact 12%, private normal conductor 163, through the winding ot the switching relay 160 ol the line switch C, and thence through the winding of the motor magnet 161 to battery. Only the relays 59 and 100 are energized over this circuit. The relay 5S in the connector l-l is marginal and does not energize in series with the windings oil' the switching relays ot the line switches. rlhe switching relay 100, ot the line switch Q, upon energizing, only-partially attracts its armatures, that is enough to disconnect the line ot the substation A trom its normal battery and ground connections. This operation is brought about by a mechanical interlocking device controlled by the arma-7 ture ot the line relay 162.

ln the connector H, the switching relay 5), upon operating, establishes a locking circuit for itself at armature 106, at armature 10T places ground upon the test Contact ll Vassociated with the substation A in order to render the called line busy, opens the circ-uit ot' the rotary magnet (3;"at armature 108 and at armatures 105 and 100 completes the signailing circuit. Ringing current 'from the generator Gen. is now intermittently projected out on the called line until an answer is obtained.

vWhen the called subscriber at substation fr removes his receiver a circuit is complet-ed t'or the ring cut-ott relay llpon energizing, this relay establishes a locking circuit ifor itsel't' at armature at armatures 84tand S0 opens the ringing circuit, and at the front contacts of these armatures linally completes the, talking connection. Conversation may now be carried on between the subscriber at substation il and the subscriber' at substation A over the heavy conductors, talking current being supplied to the calling substation troni the windings ol the line relay 50 ol the cpnnertor ll and to the called station from the "indings ot the impedance coil 53.

'When the conversation is vterminatedbolli the calling and the called subscriber will replace their receivers upon their respective switch hooks. rlhe release ot the connection is brought about by the replacement ot the receiver at substation A. When this receiv r is replaced, the circuit ot the line relay 50 is opened and this relay deenergizes thereby opening the circuit oit its associated slow acting releaserelay .31. Upon deenergizing. the latter relay at its armature 08 con'ipletes the circuit ot the release magnet 31 ot the connector ll and at its armature (ST removes ground trom the release trunk conductor il?) thereby opening the holding circuit ot the switching relay 15 in the line switch C. The release magnet (31, upon operating, restores the connector H to normal position in the usual manner. The dee'nergization ot relay 'l5 restores the line .switch C to its normal condition.

The operation ot the apparatus when one subscribei.I in the private autoiiiaticexcliange calls another' party therein haring been described, the operation when a connection is exteiided lfroni a local subscriber to a called party in the main exchange will new be subscribed. For this purpose it will. be assumed that the subscribeirat substation fr desires to extend a connect-ion to a sub scriber in the main exchange. ln order to do this Athe calling party will remove his receiver, operate his calling device for the digits O2 and thereal'ler the directory number ot' the desired subscriber in the` main "exchange lVhen the receiver removed at substation ltr the line switch C operates in the same manner as heitere described to select an idle trunl; line and extend the calling subscriberie,y line thereore lt will be assumed that the trunk line shown in the drawings extending to connector ll is the one user. villien the line ot substation il is extended to the con nec-tor H the line relay 5t) iii'nnediateiy1 energized over the calling line loop and operates to close the circuit. ol' the slow acting release relay 51. rlhe latter relay tano tions in the usual manner to prepare the impulsing circuits oif the connector ll and to place ground upon the release trunk con ductor el) thereby establishing a. holding cir-- cuittor the line switch C. All the operations outlined above have already been described in the preceding connection and will be readily understood.

ln response to the tirst operation ot the calling' device S at substation il the line relzj 5t) controls the operation ot the vertical magnet o() in stepping Vthe switch shaft carrying the switch wipers i12-11%, inclusive, opposite the tenth level ot baul: contacts. ll'hcn the switch wipers are brought opposite the tenth level, a cani on the switch shalt causes the shal't springs 8O and S1 to be iorced into engagement with their worl-:ing

contrats.V By the operation ot spring 81 a circuit coinileted extending trom ff-round Y through the winding et the relay 54E, by way upon operating, establishes a l clingi circuit 'tor itselit' at armature (33, disconnects the hattery and ground connections troni the wind ings oil the impedance coil 58 and connects the two windings in series across the talking conductors at arn'iatures 82 and 83, thereby preparing another pointin the previously mentioned repeating circuit. rlhe slow acting relay 52 maintains its armaturesbatlracted throughout the vertical movement ot' the switch Vand at its termination deener gizes preparing a circuit tor the rotary magnet (i2.

l'Viren the calling device at substation A operated in accordance with the digit 2, two impulses ot current are sent to rotary magnetv (S2. lilagnet 62 operates to rotate the switch 'iipers into engagement with the second set ot bank contacts in the tenth level. The slow acting relay o? is energized in multiple. with the rotary magnet and operai'es at its arnature 92 to connect the test wiper 113 to the test relay 56 and at its armature Oil short circuits the springs controlled by arinature 8S on the test relay. lt the trunlt line associated with the second set of bank contacts on the tenth level is busy ground 'will be connected to the test contact fed by `die test wiper 113 and test relay l be energized. Upon energizing, relay 5G at. armature 87 establishes a locking circuit Ylor itselt' and at armature 88 coirpletes the circuit ot the rotary magnet 62 over a path extending trom ground on releafee tunlt conductor 49 by way ot shaft Led spring 8O and its working conl i (j contact of spring 73 and the spring, baclt contact and armature il, t contact and arn'iature 96, armature. S25 its `lrontcont-act, armature 108 and its the rotary magnet (32 to battery. Magnet G2 el crates to rotate the s yitch wipers into ene' ement with the next set o' bank contit-cts on Vthe tenth level and at its arniature 9?) opens the locking circuit ot the test relay 56. lt will be noted that the slow acting relay 5i' maintained energized by a circuit in the multiple with the rotary magnet. rlest wiper 113 is thus maintained in connection with the test relay 56. By the operation ot 'the rotary magnet the circuit ot' relay :3G opened and this relay deenergizes, opening the circuit ot the rotary magnet, which deenergizes also. It the trunk line associated with the next set of banli contacts is busy, the relay .is again energized and operates, to close a locking circuit i''or itself and to con'iplete the circuit of the rotary magnet Magnet G2 operates. as heitere, to open the. circuit et the test relay and to advance the switch wipers another step into engagement with the next set ot bank contacts. 'llhe alternate operation ol' the relay 5F and the rotary magnet G2 continies until an idle t "unl: tound which we will asf-aime is the trunk line shown in the drawings comprising conductors 1&0 and 142 and terniinating in the bank contacts 11S- 120, inclusive. "When the switch wipers are brought into engagement with this set ot bank contacts there will be no ground connected to the test contact 119 and the test relay 56 will not be again energized. Howett) ever, immediately after the deenergization of the slow cting relay 57 a circuit is completed which extends over the following path: ground on release trunk conductor 19 through armature 8T and its back contact, through the upper windings ot' the ielays 59 and 5S, back contact and armature 92, normally closed springs controlled by armature 10T, test wiper 113,. test contact 119, and through the resistance R to battery. On account ot the marginal adjustment of relay 58 only the relay 59 is operated over the above circuit. Upon operating, the latter relay places ground upon the test contact 119, establishes a locking circuit for itself, and at armatures 105 and 109 places a bridge across the trunk conductors L10 and 142. T his bridge may be traced from trunk conductor llt), by way ot' bank contact 11, wiper 112, front contact and armature 105,y armature Si and its front contact, armature 91 and its back contact, through the upper winding ot the impedance coil 53, armature 82 and its front contact, front contact and arn'iature 83, through the lower winding of the impedance coil 53, armature titi ot line relay 50 and itsA trent contact, front contact and armature. S6, armature 109 and its :tront cont-act, wiper 11i, bank contactl 120, to trunk conductor 142. rlhe above traced bridge or repeating circuit immediately causes the operation ot the line relay in the incoming selector switch in the main exchange which closes the circuit ot' its associated slow acting release relay. rlthe latter operates to prepare the operating circuit of the incoming selector switch. The trunk comprising` conductor 1%() and 142 may terminate at the main exchange in a line switch similar to the line switch C. yl`his line switch` will then, ot course have access to lirst selector switches in which'case the bridge or repeatingr circuit previously traced, causes the operation ot the line switch in the main exchange to extend the connection to an idle first selector switch. ln any event, in response to the digits of the called subscribers number, a series of selector switches and a connector switch are operated in the main exchange to extend the connection to the desired line. The iinpulses which control t-he switches in the main exchange are repeated by the connec` tor H, as at each deenergization ot the line relay 5t) in response to the operation oit the calling device S the bridge across the trunk conductors llt) and 1&2 is opened at armature be. ltwill be noted that during each series of impulses the slow acting relay 53T is energized and maintains its armature attracted throughout the series. rlhe operation ot relay 5T serves to remove the impedance coil 553 .trom the bridge or repeating circuit and closes a direct bridge across the trunk conductors 1&0 and 1l?, through the armature 6Gv on the line relay 50.- The'operation of the'antomatic switches in the main exchange takes'place in a well known manner.

lVhen the conversation is terminated the release of the connection is brought about by the replacement otl the receiver at substation A in the usual manner.

The usual operations o'l the private automatic exchange system -when a local call is made and when a to a subscriber in the main otlice having been described, the operation of the apparatus will now be described when the exchange is enlarged to take care of 180 lines. It is necessary, in order to enlarge the private automatic exchange, to provide an additional group ot line switches similar to line switch C so that each added subscribers line may terminate in one ot these line switches. Another group ot' connector switches, similar to the connector switch H, will also beA installed and made accessible to the added group ot line switches by means of trunk lines in the same manner as the connector H- is accessible to the line switch C. ln addition, lin order to enable a subscriber, accessible to one group ot' connector switches, to call a subscriber accessible to the other group ot' connectorl switches, the trunk lines leading to connector switches in one group are niultipled into setsl ot' bank contacts in the normal level of bank contacts in the other group otl connector switches. This is shown in the drawings in connection with the connector H, the bank .contacts 15012, inelusive` being the 'set ot contacts associated with theY trunk line extending to the .connector l-l in the normal level ot' the added group ot connector switches. The trunk lines leading to connector switches in the same group as is the connector H are multipled in the normal level ot the connectors in the other group in this same manner.

The connector switches in the group in.

which connector ll is located will, inthe same manner, havel access to trunk lines leading to the added group ot connector switches. For handling outgoing connections more trunk lines to the main exchange may be installed and made accessible from the tenth level oi the added group ot' connector switches, or it' there are enough trunk lines already accessible to the connector H and the other switches of its group to handle all the out going tratlic ot the new group ot lines. the trunks accessible from the tenth level of the connectors such as H will be merely multiplied into the tenth level of the new group of connector switches.

In the enlarged system local connections between subscribers in the saine group and out going calls to the main otlice will be handled in the saine manner as has already been described. However, the operations connection is extendedY of the connectors are somewhat different than have been previously described when the call is extended from a subscriber in one group to a subscriber in the other group. In order to describe this operation, it will be assumed that the subscriber at substation A desires to call a subscriber whose line is accessible to the other group of connector switches. To accomplish this result the subscriber at substation A will remove his receiver. operate his calling device S for the digits O1 and thereafter the two digits of the local subscribers number in the other group.

Then the receiver is removed at the calling substation A, the line switch C operates in the same manner as before described to extend the calling subscribers line over a trunk line to an idle connector switch. It will be assumed that the trunk line shown in the drawings is the one selected by the line switch C. Immediately upon the extension of the calling subscribers line, the line relay of the connector H is energized and operates to close the circuit of the slow acting relay 51. The relay 51 operates to prepare the impulsing circuits of the connector H and to place ground upon the release trunk conductor L19. rIhis latter operation serves to establish a holding circuit for the switching relay of the line switch C in order to maintain the said relay energized throughout the connection.

In Vresponse to the operation of the calling device S for the digit O the -line relay 50 controls the operation of the vertical mag net in raising the switch shaft carrying the switch 'wipers 112-114, inclusive, opposite the tenth level of bank contacts. When the wipers are brought opposite the tenth level, the shaft controlled springs and Y 81 are operated into engagement with their working contacts and the relays 54 and 55 are energized as before and with the same results.

lVheu the digit 1 is dialed, one impulse of current is sent to the rotary magnet 62 and the switch wipers are brought into engagement with the first set of banlr contacts on the tenth level which are shown in the drawings at 115-117, inclusive,

The test contact 116 associated with this set of bank contacts is connected to battery through the low resistance R. New, immediately upon the deenergization of the slow acting relay 57, which is energized in multiple with the rotary magnet, a circuit is completed for the upper windings of relays 58 and 59.

Due to the low resistance of as conipared with the resistance of the switching relays of the line switches and resistances 'such as It', the marginal relay is energized in series with the relay 59. Relay 5S, upon operating, establishes a loclnngcircuit for itselfl to ground through off normal spring 72 and its working contact at armature 95, at armature 98 closes the circuit of the relay 56 and at armature 911- opens a point in the locking circuit of the switching relay 59. Further results of the operation of relay 58 are that at armature 96 a point in the circuit of the rotary magnet 62 is openerL and at armature 9'4" a circuit is closed for the release magnet 61. As the locking circuit of relay 59 is opened at armature 9ithis relay does not remain energized. Relay 56, upon operating, opens the circuit of the upper windings of the relays 5S and 59 at armature 87, at the front contactv of this armature establishes a locking circuit for itself, and atarmature 88 prepares the rcuit of the rotary magnet 62. The release magnet 61 of the connector H operates to restore the switch shaft carrying the switch wipers to normal position thereby bringing the said wipers opposite the normal level of bank contacts. When the switch shaft reaches its normal position the circuit of the release magnet 61 is opened as is the locking circuit of the relay 58 at the off normal springs. The latter relay deenergizes and at its armature 9S opens the original energizing circuit of the relay 56, at armature 97 opens another point in the circuit of the release magnet, at armature 94 prepares a point in the locking circuit of the switching relay 59, and at armature 96 completes a circuit for the rotary magnet 62 over the following path: ground by way of otl normal spring 72 and its resting contact, resting contact of spriirr 73 and the said spring, back contact and armature 74, back contact and armature 96, armature 88 and its front contact, armature 108 and its back contact, and thence through the winding of the rotary magnet 62 to battery. The rotary magnet operates to rotate the switch wipers into engagement with the rst set of bank contacts on the normal level and at its armature 99 opens the locling circuit of the relay 56. Relay 56, upon re 'acting its armatures, opens the circuit of the rotary magnet which innndiateljV dcenergizes. It will be observed that the slow acting relay 5T is cnergfzcd in multiple with the magnet 62 and operates to connect the test wiper to the test relay 56. Upon the first rotary step of the switch shaft. the rotary olf normal spring 66 is caused to engage its working Contact thereby preparing a circuit for the release magnet 6.1,. lf the first trunk line on the normal le ed'ending to connector switches, in the other ,u onp is busy, there will be ground poten` tial present upon the test contact engaged. by the test wiper 113 and the test relay :26 will le immediately energi'fzed. its before, relay 56 operates to establish a locking cir cuitfor itself and to close` the circuit of the Sii lll() rotary magnet. Magnet 62 advances the switch wipers into engagement with the next set of bank contacts and opens the circuit oi the relay G which deenergizes opening the circuit of the rotary magnet which dc.- eiieigizes also. The alternate operation ot the relay 56 and rotary magnet G2 continues the other group.

until the switch wipers are brought into engagement with a set ot bank contacts associated with an idle trunk line extending to a connector switch in the other group. lt will be assumed that the trunk line shown in the drawings terminating in bank contacts 12S-1230, inclusive is the one selected by the connector H. Then the switch wipers are rotated into engagement with this set ot iaiilr contacts, there being ne ground potential present upon the test contact 129, testrelay 5G is not again energized and the rotat'on ot' the connector H ceases. rllien, upon the deenergization et the slow acting relay 5T, a circuit is closed tor the switching relay 5i) over the following path: groi'ind on release trunk conductor a9 by way otl armature ST and its back contact, through the upper windings of relays 59 and V58, back contact and armature 92, normally closed springs controlled by armature 10T, testwiper 113, test contact 129 to release trunk conductor 136. Release trunk conductor 136 extends, in the same manner as the release trunk conductor 49, through an armature and back contact on the slow acting relay in the selected connector switch and through a resistance such as R2 to battery. rlhe resist-ance R2 is suihciently high so that the relay 5S is not energized though the switching relay 59 is opera-ted. TUpon operating, relay 59 establishes a locking eircuit'tor itselia at armature 10G, at armature 108 opens the circuit of the rotary magnet, at armature 10T places direct ground on the release trunk conductor 13G, and at armatures 105 and 109 closes a repeating circuit Jr'or cont-rolling the line relay et' the sezed connector switch in lt will be noted that the relays 5l and remain energized even after the operation of the release magnet G1 as ground has not been removed trom the release trunk conductor L19. rlhe repeating circuit above referred to may be traced from the trunk conductor 13T, bank contact 128, wiper 112. front contact and armature 105, armature Set and its front. contact, ai'inat til and its baci; contact, through vthe upp winding et' the impedance coil 53, arnia'tu e e2 and its front contact, trent contact and armature through the lower winding ot' the impedance cod armaturete and its Vtrout contact, front contact and armature S6. armature 10i) and its trent contact, vper the, bank contact 13:30. to t-runl-z conductor 1.-. The line relay of sei. d coi'inector switch inmiediately energized over this repeating circuit and operates to close the circuit ot its associated slow acting release relay.- x

lfhen the calling device at substation A is operated tor the two digits ot the desired called subscribes number the seized connector in the other group will be operated, in a manner similar to the connector ll when it was used in the local connection, to extend the vcall to the desired line. rlhe line relay oi the connector l-l controls the operation ot the'connector switch in the other group in the samer manner as has been described when the connection was extended to .a main exchange subscriber.

llhen the conversation is terminated the release ot the apparatus is brought about by the replacement otl the receiver at substation i in the usual manner, that is, the line relay 5t) is deenergized and opens the circuit ot the line relay et' the seized connector switch and also the circuit of the slow acting relay 51. The deenergization ot relay'` 51 coinpletes the circuit ot the release magnet G1 and removes ground trom the release trunk it). li'lagnet (3l operates to restore connector H to normal. The removal of ground from the release trunk conductor 4:9 causes the deenergization et' the relays 59, 55 and` 54 and in addition the deenergization et the switching relay 15 ot the line switch C. deenergizatien of the line relay of the connector in the other group opens the circuit ot' its associated slow acting release relay thereby causing the operation ot the release magnet to restore the conector to normal. In the above manner all the apparatus used in the connection is restored to its normal posit-ion.

'lhe manner in which a. call is made to a subscriber whose line is in a group other than' that ot the subst-ation A having been described it will be perfectly apparent that when a subscriber in the other group desires to call a subscriber whose line is located in the saine group as that ot the substation A he will prelix the digits O1 to the number which would be called were the subscriber in his own group the one called. It will be appreciated that itis quite desirable to so group the subscribers that most ot the calls will be local to each group when a 18() line system et this type is originally installed. lVhen a line private automatic exchange is enlarged in this manner to lines the calls have a tendency to be naturally divided so that the majority are local to each group.

rthe Ytea-.tures ot the invention having been described and ascertained what is considered to be new and desired to have protected by Letters Patent will be pointed out in the appended claims.

What l claim as my invention is: 1. in a telephone system, an automatic switch, telephone. lines and trunk lines accessible lo said switch, means tor seizing said switch and `lor operating it in accordance The i lil?) with the digits et a called nun'iber to connect; with one oi said telephone lines, and means automatically operative responsive to an operation ot said switch in accordance with a predetermined nuniber tor releasing said switch and for causing it to select an idle one o'l said trunlt lines.

2. In a telephone system, an automatic switch, telephoneV lines accessible to said switch, means for seizing said Iswitch and Ytor operating it only in a cordance with two digits of a called number to connect with one ol said telephone lines, means automatically operative it said switch is operated in accordance with a predetermined two digits 'for causing its release, and other telephone lines accessible to said switch in its vertically released position without calling any additional digits.

3. In a telephone system` a telephone line, an automatic switch, trunk lines accessible to said switch, means tor connecting said line and said switch, releasing means tor said switch to restore it to normal atter it has becnoperated, a calling device on said line, means :tor operating said switch in response to two operations ot said calling device before operating said releasing means, and means then automatically operative for causing the operation ot' said releasing ine-ans and for initiatingl the trunk selecting operation ol said switch.

a. In a telephone system, an automatic switch` trunk lines accessible to said switch, means tor seizing said switch and 'tor operating it in accordance with a digit ot a called number. means operative it said switch operated in accordance with a predetermined digit tor restoring it to normal. and means operative when said switch reaches its normal position tor automaticallyVT causing it to select an idle one ot said trunk lilies.

ln a telephone system, an automatic switch trunk lines and telephone lines accessible to said switch. divided into groups, means ttor seizing;- said switch and 'lor operating it in accordance with a digitot a called number in one plane to select a group of .said telephone lines and in accordance with another digit oi said called number in another plane to select a line in a group` and means operative il the second digit corresponds to a predetermined one for restoring iid switch to its initial position and tor causing` it to automatically select an idle one ot said trunk lines.

G. in a telephone system, two groups ot connector switches. a normal level ot bank cont-acts 'for every connector in each group, a. wiper set lor each switch normally associated with its normal level o'tl bank contacts, and trunk lines connecting the bank contacts Yot said normal levels with the connectors ot the other `group.

T. ln a telephone system, two groups of connector switches, telephone lines accessible to the connector switches of each group, means for seizing a connector in one ot' said groups and for operating it in accordance with the digits of a called number to connect with the corresponding accessible telephone line, trunk lines accessible to each group of connectors leading to switches in the other group, means operative only'i'f a certain number is called for releasing said switch after the same is operated and for then causing the switch to elect an idle one of said trunlr lines leading to a connector in the other group, and means l'or then operating the seized connector to extend a connection to one of said telephone lines.

8. In telephone system, two groups ot connector switches, telephone lines accessible to cach group of connectors, a normal level for every connector in each et' said groups, trunk lines extending from the normal levels of the connectors of one group to the connectors of the other group, and means controlled trom one o1 said telephone lines for seizing a connector switch of one group and tor operating it a connector to connect with one of said accessible telephone lines or as a selector on its normal level to extend a connection to an idle connectorin the other group.

t). ln a telephone system, two groups et connector switches, telephone lines accessible to each group o't connectors, a normal level for every connector in each of said groups, trunk lines extending from the normal levels of the connectors ot one group to the connectors of the other group, means controlled from one ot' said telephone linesl for seizing a connector switch of one group and for operating it as a. connector to connect with one of said accessible telephone lines or as a selector on its normal level to extend a connection to an idle connector in the other group, and means for then operating the seized connector to extend the connection to one of said accessible telephone lines.

l0. An automatic switch having directive movement and an automatic hunting movement, both starting trom normal position, and means responsive to a directive movement of predetermined extent for restoring the switch and starting the hunting movement.

ll. ln combination, an automatic switch, trunk lines accessible to said switch, means for operating said switch, and means responsive only to an operation of predetermined extent for releasing said switch to normal and tor causing it to auton'iatically select an idle one of said trunk lines.

l2. An automatic switch having bank contacts and wipers normally dissociated therefrom, banlt contacts with whichsaid wipers are normally associated, means for advanc- Sti llt)

lla'i lli?) ing said wipers to any desired set of normally dissociated bank contacts, and means responsive only to the advance of said wipers to a particular set of such contacts for restoring said wipers and for advancing them automatically over the normally associated bank contacts.

13. In a telephone system, an automatic switch, trunk lines divided into two groups accessible to said switch, means tor eizing said switch and for directively controlling it-s operation to associate it with one or" said groups of trunk lines, releasing means for said switch, means operative itl a certain predetermined digit is sent to said switch for initiating a trunk selecting operation in the group. with which it is associated, and means operative if a different predetermined digit is sent to said switch tor operating said releasing means and for causing said switch to select a trunk line in the other group.

14. In a telephone system, an automatic switch, trunk lines accessible to said switch divided into groups, means for seizing said switch and for operating it in accordance with a digit of a called number in one plane to associate it with a group ot' said trunks and in accordance with another digit ot said called number in another plane for causing it to automatically select an idle trunk in said group of trunks, and means operative if the second digit corresponds to a predetermined one for restoring said switch to its initial position and for causing it to automatically select an idle trunk in another group ot' trunks.

l5. In a telephone system, a trunk line, other 'trunk lines, a directive device operable over said first trunk line and having a normal position, and means responsive to a directive movement of said device of a predetermined extent for releasing said device and for automatically connecting said trunk line to an idle one of said other trunk lines.

16. In a. telephone system, an automatic switch having wipers, groups of lines accessible to said switch, means responsive to the dialing` 'of a digit of a called number for positioning the wipers of said switch opposite one group of lines, and means responsive to the dialing of another digit of a called number for releasing the wipers and tor positioning the same opposite another group ot lines.

In witness whereof, I hereunto subscribe my name this 2d day of March, A. D. 1922.

JOHN n. GARDNER. 

